1. Field of the Invention
The present invention is generally related to wireless broadcast transmissions and more particularly to a method for providing an increased level of assurance for multicast packet delivery.
2. Description of the Related Art
Group transmissions are typically used to deliver a message to a group of receivers simultaneously. A group packet is any packet wherein the address is a multidestination address, associated with one or more stations on a given network. The type of group includes, but is not limited to, a multicast group or a broadcast group. The designation of which group is to receive the message is ordinarily identified by the MAC sublayer address of the packet. A multicast group address is an address associated by higher-level convention with a group of logically related stations. A broadcast address is a distinguished, predefined multicast address that always denotes the set of all stations on a given LAN. This group is predefined for each communication medium to consist of all stations actively connected to that medium; it is used to broadcast to all the active stations on that medium. All stations are able to recognize the broadcast address. It is not necessary that a station be capable of generating the broadcast address.
Typically, an Access Point sends a multicast transmission after waiting a specified amount of time for a channel to be clear. Normally the message is sent once and there is no mechanism for determining if any receiver actually received the message. The multicast package may be lost due to a collision with another transmission, or due to bit errors caused by interference or channel noise.
One approach to increasing the reliability of multicast messages has been to send the multicast message to each receiver individually. As each receiver receives the message, it sends an acknowledgment. While this method improves delivery of the message, a major disadvantage is that it uses up an enormous amount of bandwidth because of all of the additional traffic generated by resending the same message numerous times, the time waiting for an acknowledgment for each transmission, and the time required for each acknowledgment to be transmitted. For example, if there are N stations, then each broadcast/multicast packet must be sent N times, and N acknowledgments must be transmitted. Each directed broadcast packet must also be retransmitted if the acknowledgment is not received.
Thus, there exists a need for a method that can improve the reliability of group message delivery with low bandwidth requirements.
Additional objects, advantages and novel features of the invention will be set forth in part in the description which follows, and in part will become apparent to those skilled in the art upon examination of the following or may be learned by practice of the invention. The objects and advantages of the invention may be realized and attained by means of instrumentalities and combinations particularly pointed out in the appended claims.